It is known to place a cell suspension in a generally tubular sample chamber having an open end juxtaposed to the surface of a microscope or like slide, with the interposition of an apertured filter card that both provides a seal between the sample chamber and the slide surface and also serves to absorb the liquid components of the suspension. The assembly of sample chamber, slide and filter card is subjected to centrifugation to cause the deposition of a layer of cells on the slide surface and the removal of the suspension liquid into the filter card. One example of cytocentrifugation apparatus especially adapted to perform this cell separation and deposition technique is disclosed in U.S. Pat. No. 4,391,710.
The cell suspension that is submitted to centrifugation generally requires some preparatory treatment, especially when it is desired that the centrifugation shall produce a monolayer of deposited cells uniformly dispersed over a relatively large receiving surface area so as to be suitable for automated examination by optical scanning devices. Thus typically cell samples obtained by scraping ("smear") techniques are collected in specimen containers that are filled with a collection fluid to preserve the cells while in transmit from a collection centre to a laboratory. When the collection containers are received by the laboratory the cells of the specimens therein have usually aggregated and need, therefore, to be disaggregated, for instance by stirring in the collection fluid. This leads to a relatively small quantity of cells becoming dispersed in a relatively large volume of collection fluid and it is necessary to allow the cells to settle to enable a suitably concentrated sample to be obtained for the centrifugation procedure. This settlement may, for instance, be accomplished by precentrifugation to form a packed cell button, a sample of which may be then taken as by pipette, diluted with a suitable volume of suspending liquid and then placed in the sample chamber of the centrifuge.
These preparatory sample treatment procedures are time-consuming and labour intensive and by their nature can easily lead to dissociation of a particular cell specimen from the records relating to the donor patient.
A further and more specific object of the invention is therefore to facilitate the carrying out of these preliminary procedures, as necessary for any particular type of cell specimen, and to minimise the risk of misidentification of the donor or source of a particular cell deposit as produced by the centrifugation.